This invention relates in general to communications outlet boxes and, more particularly, to outlet boxes for fiber optic and low voltage communications cables.
In this information age, the consumer""s seemingly insatiable demand for increasing bandwidth is pushing the communications industry to provide ever-larger information xe2x80x9cpipesxe2x80x9d into the user""s home or business. It is predicted that soon the demand for unlimited bandwidth will exceed the capacity of electron-driven information delivery systems. Light- or photon-driven information delivery systems, such as fiber optic cable systems, are being used more and more to meet the consumer""s demand for instantaneous access to information, entertainment, and communications.
Optical fiber cable has already replaced metallic cable in the backbone networks of most local and long-distance telephone carriers, cable television operators, and utility companies. Fiber optic cable systems are also rapidly gaining ground in commercial settings, including office buildings and factories. Optical fiber cable technology has been slower to bridge the so-called xe2x80x9clast mile bottleneckxe2x80x9d from backbone networks into residential homes and smaller businesses, however, due to high costs and slightly-lagging consumer technology demand for high bandwidth capability.
With the increasing use of high-definition television, digital consumer electronic devices, always-on Internet connections, and related digital and information technologies, however, there is a growing market demand for greater information bandwidth in the home and office. In addition to bridging the gap from commercial backbone networks to residences and small businesses, there is also an increasing demand for high-bandwidth intra-residential and intra-office communication systems, enabling, for example, high-speed home networks and multiple high-bandwidth external connections. Concurrent with the increased demand for high-bandwidth networks has been the development of new technologies and standards that are making such networks economically viable. For example, plastic optical fiber (POF) cable promises to bring down the costs of optical fiber cable and is easier to interconnect to form the network and interface with digital devices. The adoption of the IEEE-1394 1995 Standard for a High Performance Serial Bus, sometimes referred to as the FireWire standard, is also playing an important role in enabling economical high-bandwidth systems. FireWire is on its way to becoming the standard method of connecting digital audio and video electronic devices to personal computers.
The introduction of fiber optic cable networks into homes and small businesses requires, inter alia, the installation of individual fiber optic communication outlet boxes, typically in multiple locations, such as individual offices, for connecting to the fiber optic cable network. The installation of optical fiber cable, however, presents different physical requirements than does the installation of conventional copper wire cable. Conventional outlet boxes designed for copper wire cable applications are not optimal for use with optical fiber cable systems. Optical fiber cable can be damaged if the cable is bent or coiled with a radius of curvature smaller than a minimum bend radius. A typical minimum bend radius for an optical fiber cable is approximately 50 mm, or about two inches. Conventional outlet boxes are four inches square, one and one-half or two and one-eighth inches deep, and therefore can only just barely accommodate the typical minimum optical fiber cable bend radius of two inches (four inches in diameter) with no margin to facilitate installing the optical fiber cable into the outlet box.
When installing copper wire cable systems, the bending radius of the wire is generally not a concern. It is typical for installers to make the required electrical connections and then force any excess cable into the junction or outlet box prior to installing the outlet box cover or fixture. This practice is not desirable for optical fiber cable systems due to the sensitivity of the optical fibers to the bending radius. It is desirable and common practice, however, to include some extra length of optical fiber cable in the outlet box so that if the fixtures are replaced in the future, or if the cable fibers are damaged, a section of optical fiber cable may be removed and sufficient cable will remain to make the desired connections. Some means for maintaining the optical fiber cable minimum bend radius in the excess cable is desirable for optical fiber cable outlet boxes. It is particularly desirable to provide such means in fiber optic cable outlet boxes as this technology becomes more wide spread, because less specialized workers and home do-it-yourselves will increasingly be installing fiber optic cable systems.
One common method for providing extra room in prior art outlet boxes is to add an extension onto the front of the outlet box, that extends out from the main body of the outlet box. While this method provides a larger volume to store optical fiber cable, it does not provide a means for ensuring the stored cable is maintained in a coil having a radius larger than the minimum bending radius of the optical fibers forming the cable. Also, the resulting fixture will frequently and undesirably project out from the wall into a room, which may be inconvenient, hazardous and/or aesthetically unappealing, and may expose the outlet box to unnecessary jostling and impacts.
A fiber optic cable junction box that maintains a large bending radius for optical fiber cable located in the junction box is disclosed in U.S. Pat. No. 5,661,840 to Caveney. This patent describes a junction box with removable clips 26 and spools 27 for positioning and arranging fiber optic cables. The spools presumably are larger in radius than the minimum bend radius of the optical fiber cable. This design, however, requires a large junction box, because the cylinders fill a large portion of the volume of the box. The cylinders limit the volume available for other purposes and may get in the way of the installer.
U.S. Pat. No. 4,717,231 to Dewez et al. discloses a distributing box for optical fiber cable that comprises a first receptacle 10, a second receptacle 11 and a movable panel 12 therebetween. The movable panel includes four U-shaped gulleys 124 holding the fibers in a curvilinear bundle with a minimum bending radius r=50 mm. The disclosed gulleys, however, xe2x80x9care oriented toward the interior of rear compartment 100.xe2x80x9d The gulleys disclosed by Dewez et al. therefore, function to hold the optical fiber cable and limit the maximum radius of the fiber cable, but not the minimum bending radius. For example, if the exterior portion of the cable is pulled, the gulleys would not prevent the optical fibers from tightening up to less than the minimum bend radius. European patent No. 0 293 183 (Bylander) discloses an optical fiber cable distribution panel having a cover 80 with a plurality of fiber retaining lips 85, 86, and 87 formed therein to retain slack fiber cable, as seen most clearly in FIG. 8. The disclosed lips, are generally formed with the lip facing inward, similar to Dewez et al.""s disclosed invention. The retaining lips function to hold the optical fiber cable when the cover is opened and closed, but again will not prevent the cable from tightening into a loop smaller than the fibers minimum bend radius.
U.S. Pat. No. 5,966,492 to Bechamps et al. teaches an apparatus for storing and splicing optical fiber cable, having a tray 10 that slidably mounts to a cabinet 32 for holding and splicing optical fiber cables. The tray includes a portion for storing optical fiber cable that has a number of retainers 16, 17, 18, and 19 for retaining extra optical fiber cable. Although Bechamps et al. states that the retaners prevent the cable from being bent beyond its minimum bend radius, it appears from examining FIG. 4 and FIG. 5, and the disclosure contained at column 4, beginning at line 25, that the retainers will not limit the minimum bending radius of the optical fiber cable. In particular, as in the disclosures above, if the optical fiber cable external ends are pulled, the retainers will not impede the cable coil from reducing its coiling radius below the fiber""s minimum bend radius.
These prior art patents are generally directed to large, free standing or externally-mounted, cabinets, which are normally referred to as xe2x80x9cpatch panelsxe2x80x9d within the communications industry. As optical fiber cable begins to be installed to individual offices within an office building of any size, an xe2x80x9cin-wallxe2x80x9d optical fiber cable outlet box will be desirable. As noted above, conventional electrical outlet boxes, which are four inches square in cross-section, are only marginally large enough to accommodate fiber cables having a minimum bend radius of two inches. Because optical fiber cable must be manipulated when it is inserted into the outlet box, and making the appropriate connections, it is desirable that an optical fiber cable outlet box be larger than four inches square in cross-section, but still be small enough to fit within a conventional wall, and installable by conventional means such as a bar hanger or side bracket.
U.S. Pat. No. 5,721,394 to Mulks discloses a flush-mountable junction box, for use with fiber optic communications cable. Mulks describes a box wherein the optical fiber cable enters the top of the box 1, and pass through a strain relief member 4, and is connected to panel 7 mounted connectors 17. No means are provided to maintain a cable radius that is greater than the minimum fiber optic bend radius. The connection box disclosed by Mulks has the disadvantage of being significantly larger than conventional electrical outlet boxes and would require a large hole be cut into the wall to install the box. Mulks also teaches leaving the connection box open on one side, for the passage of cable therethrough. However, this leaves the interior of the box susceptible to intrusion and damage by insects and/or small nuisance animals.
For the foregoing reasons, there is a need for a fiber optic cable outlet box that has a means for retaining cable with a preselected minimum bending radius, and in particular with a minimum bending radius greater than two inches. There is also a need for such an outlet box that is installable so as to be generally flush-mounted in walls in a manner similar to conventional electrical outlet boxes, and wherein the outlet box cooperatively provides a generally enclosed and protectet volume.
The present invention is directed to an outlet box that satisfies the needs discussed above. More specifically, the invention is directed to providing a communications outlet box that is particularly suited for applications that include optical fiber cables. The invention is directed to an in-wall outlet box that is larger than conventional in-wall outlet boxes, and includes a means for retaining extra cable in the outlet box while maintaining a predetermined minimum bending radius.
According to one aspect of the present invention, the fiber optic communications outlet box comprises a rear panel approximately five inches square, four generally rectangular side panels, not more than two and seven-eighths inches wide, that cooperatively with the rear panel form a box having an open face, tabs extending inwardly from the side panels, and cable retainers extending inwardly from the rear panel about which a cable may be coiled and that are spaced to maintain a minimum bending radius in the cable of not less than about two inches.
According to another aspect of the invention, the cable retainers are generally L-shaped, with the first leg of the retainer that is connected to the rear panel having a curved profile whereby a cable coiled around the cable retainers will not encounter a sharp edge.
According to another aspect of the present invention, the communications outlet box further comprises an extension ring that partially covers the open face of the outlet box, and includes a rectangular extension sized to match the thickness of the wall panels into which the extension ring will be installed, and adapted to have a fixture such as a fiber optic connector strip attached to the extension ring.